1. Field of the Invention
The present invention relates to a fuel cell which is comprised of an electrolyte/electrode structure having an electrolyte being arranged between a pair of electrodes, and separators which are stacked on the electrolyte/electrode structure, and include reaction gas passages for feeding the reaction gas in the surface direction of the electrodes, said reaction gas being provided from the reaction gas introducing communication holes to the reaction gas discharging communication holes of which gas flaw is extending at least in the stacking direction.
2. Description of the Related Art
In a solid polymer electrolyte fuel cell, for example, an 15 electrolyte/electrode structure, in which an anode electrode and a cathode electrode are juxtaposed on both sides of an electrolyte (or an electrolyte membrane) which is made of a polymer ion-exchange membrane (or an anode ion-exchange membrane), and said electrolyte/electrode structure is damped by said separators. The fuel cell of this kind is used as a fuel cell stack by stacking plural sets of the electrolyte/electrode structure and the separators for a predetermined number. In this fuel cell, the fuel gas fed to the anode electrode, such as a gas containing hydrogen in main (as will also be called the “hydrogen containing gas”), has its hydrogen ionized on an electrode catalyst so that the hydrogen ions migrate through the electrolyte toward the cathode electrode. The electrons generated during said process are extracted through an external circuit to be utilized as DC electric energy Moreover, since the cathode electrode is fed with an oxidizer gas such as a gas containing oxygen mainly or air (as will also be called the “oxygen, containing gas”), the hydrogen ions, the electrons and the oxygen are reacted with one another so as to produce water at the cathode electrode.
In the fuel cell of this kind, it is required for the fuel gas, the oxidizer gas and the coolant to flow air-tightly or liquid-tightly along their corresponding dedicated passages. Therefore, various seal members are usually interposed between the electrolyte/electrode structure and the separators. For example, the seal member of Patent Publication 1 (JP-A-2001-332276) is structured, as shown in FIG. 9, such that a base gasket 1 is made of an elastic material of a synthetic rubber material or synthetic resin material having a high hardness of 70 degrees to 90 degrees, and such that gaskets 2 of a synthetic rubber material having a low hardness of 30 degrees to 50 degrees are arranged on the compression surfaces of the base gasket 1.
According to Patent Publication 1, however, the seal members are assembled between the separators so that the number of assembling steps is increased, which ends up with lower workability in addition to the considerable difficulty in aligning the seal members. Moreover, since each seal member needs at least two sets of the sealing members on the both sides, which also raises a complicated structural problem.
In the method for manufacturing an integral seal type separator of Patent Publication 2 (JP-A-2002-237317), for example, there is disclosed a method of seal members being arranged on electrode reaction surfaces or outer surfaces of the communication holes, which are integrated with both sides of the separator body of the fuel cell.
This Patent Publication 2 is effective because it enables the seal members to be more precisely aligned and the number of the assembling steps can be significantly reduced, as compared to the cases of the seal members being arranged on both sides of the separator body, or coating the sealing material beforehand.
As for the seal members generally used in the related arts, they are formed into a hill-top shape (i.e., a lip shape). Therefore although the seal members are integrated with the separator body, as disclosed in Patent Publication 2, the sealing properties may be eventually deteriorated in case of mounting a fuel cell into the vehicle.
More specifically, the leading end portions of the seal members might be displaced by the vibrations generated during the running time or the shocks caused by an abrupt stopping or starting of the vehicle. In such a circumstance, it becomes difficult to keep the desired sealing properties due to the satisfactory contact area being not made. When the metal separators are used, especially, the deformation, warp or swelling may easily occur on the surfaces of the metal separators. However, the leading end portions of the seal members cannot be appropriately adjusted to the surface changes of the metal separators, which may raise a problem such that the sealing surface pressure needed for sealing function with the separator surfaces cannot be retained.
Moreover, when the stack is to be made by stacking a plurality of fuel cells, a displacement might occur readily at the leading end portions of the seal members. As a result, falling of the leading end portions of the seal members, dropping the surface pressure, reducing the contact area, or the like may occur, and it makes extremely difficult to keep the desired sealing properties.